Method of making chasers



R. E. FLANDERS METHOD OF MAKING CHASERS July 14, 1925.

Filed June 15. 1923 lfiiziera Patented-Jul! U IT-En s-T Tss PATENT OFFICE.

nitrn n rnmnns; or srmnsrrnnn, vnnnon'r, nssronon 'ro' JONES & LAMSON mom comm, or SPRINGFIELD, vnmrorrr, AconPonA'rIoN or VERMONT.

' Israel) or MAKING- cnasnns.

- Application and June 15", an. I Seri'alno. 545,514.

' To all whom it may 001mm:-

' specification.

.-.Be it known that I, RALPH Fmn'nmrs,

"a citizen of the United. States, residing at Springfield, in the county of Windsor and State of Vermont,-have invented new and useful Improvements in a Method of Mak-' ing Chasers, of which the; :following is a ,This inventionrelate's to a method of- 'mal ing chase'rs such as are used in the thread-cutting dies of automatic lathes,

screw machines and the like and relates more particularly to the method of formin andfinishing the threads thereof.

ior such chasers it is desirable to employwhat is commonly known as high speed steel Y in order-that the cutting of the threads may be as speedily effected as possible.- To obtain the full cutting power of such steel it is' n V to heat it to about 2300 Fahrenheit at which temperature the points threaded articles begin. to melt thus ruining at the desirable"Iii? .-itemperature'..

a 'This'invention; "erefore, relates to a com- .merciaLmethod of making chase'rs,

.sp'eed-steelta I tour and yet be hardened at t e :the shape of the cutting-edge. For this reasonit has been customary toharden hi h and chasers below t e proper heat so 7 material has not been obtained. When the threads are to be groundafter the harden ing it may be treated at the desirable high temperature, 'but as chaserthreads are con cave, it is not commercially practicable to grind them to their final form since inmost cases this would require grinding wheels; of smaller than commercial diameters. order to bring chaserthread the required.

concave'form, lapping be resortedto,

they may be finished to theesirabl'e high temperature. According to this invention the chasers have their'threaxls'cut in".

any suitable manner, and they are then hard; ened'at the desirable high temperature, the

- contouruof' the threads being. badly' mis shapenv thereby, .Next the chasers are a d either straight across by traversing em length atthe full advantage of the chasers whereby r -condiameter.

.' the V ine wiseofthethreada' relativetoa th grinding wheel or to the concdvity produced presenting them directly to the grinding 'wheel, or sl ghtly con'vexedby' mounting them'on a mandrel outwardly extending and rotating the'mandrel in proximity to the edge of the grinding wheel. 1 This serves to remove the arge inaccuracies produced by the heattreatment and" reduces the threads to the proper cross-section',.but they are still insufliciently accurate to obtain a proper bearing on the work. The grinding operation is only a roughing process. lhe

chasers are then lapped to accurate finished I form, the material which it is necessary to removethereby so small in amount that lapping is a commercial process.

For a more complete understanding of.

this invention reference may. be hadto the v accompanying drawings in which- F gure 1 is a diagrammatic view illustrating the grinding and lapping action corresponding to the convexity of the wheel,

where the threads are given the concavity of the threads of taps, chasers or other.

the relative diameters of the wheel, work I and lap being indicated as well as the relative positions of the wheel relation to the threads of the chaser;

Figs. '2 and '3 are similarv views. illusandlap with trating thev grinding operation so formed i as to make straight and convex threads, 5

respectively; and r Fig. 4 is an enlarged and exaggerated diagrainmatic'view illustrating the relationsof the lapped finished surface to threads which are ground straight as, in Fig. 2.

Referring first to Fi 1, the chaser is indicated atl having h to obtain the best results, but which is also of which "is indicated by the dot and das line at 2. This is of I 1 however, than the work' yvhich intended. 'Thethreaxls maybe unds'ome whati f'concave by presenting t e chaser-to as indicated b threads cut therein while it is in comparatively soft and workable condition, and then having been-hard- .enedby heating to a temperature s'uflicient the wheelie The disuflicient to spoil theycontourof therteeth. I The chaser isth'e'n presented to a grinding wheel, the periphe chasers are of. the wheel in a-subs'tantially the arrow 3 so at no turning action o the chaser rela- 'tivev to ameter of the work on which the chaser is to operate is indicated by the concentric dotted circles at 4, the size of the chaser being much enlarged in this view for the sake of clearness. This grinding operation serves to remove the large irregularities and inaccuracies of the threads caused by the high heat treatment, but since the diameters of the wheel and the work are so difie-rent, does. not form the teeth so that they will properly bear upon the work.

.VVhen this grinding has been completed,'

the contours of the threads adjacent to their cutting edges are formed more accurately to define a proper bearing on the work by means of a lap, the size of which is indicated by the dotted'circle 5 which is only a little larger than that of the work. This lapping operation takes off only a few ten thousandths of an inch and acts on work which has already been cut by the grinding wheel. The lap is therefore not required to cut under the rough scale and remove major inaccuracies'resulting from the heat treatment which would be very slow and destructive to the lap. The laps which are used are preferably formed of some soft material such as soft steel threaded and charged with emery and revolved under pressure in contact with the threads of the chaser in such a way as to remove enough material to give the desired bearing without injuring the lap or tearing out the emery particles. which are charged into its body.

In Figure 2 the same construction is illustrated except that in this case the chaser is given a traversing movement relative to the grinding wheel as shown by the arrow 6 which causes the threads as ground to be flat lengthwise. Where the chasers are so ground the action of the lap thereon is indicated in a much exaggerated form in Figure 4 where it will be noted that the portion of the thread from a to b is flat as it leaves the grinding wheel, while the forward portion adjacent to the cutting edge at 0 and between the points a and c is concave to fit the convexity of the lap. This portion from a to c is the portion which bears on the work. In Fig. 3 is shown the construction wher in the chaser is rotated while in contact with the wheel in which case the threads are left, convex lengthwise by the grinding operation. This convexity, however, should be comparatively slight and only slightly more lapping is necessary to bring the chasers to a proper bearing on the work than when the threads are ground flat as shownin Figs. and4 or concave as shown in F ig. 1

Having thus described certain embodiments of this invention, it should be evident that various changes and modifications may be made therein without departing from its s irit or scope as defined by the appended c aims. t

I claim 1. The method of making a chaser from high speed steel, which comprises forming and cutting the threads of the chaser from the unhardened material, subjecting the cut chasers to a temperature sufficiently high to cause partial melting of the points of the threads to harden the material, grinding the threads to approximate form, and then lapping the threads to a proper bearing on the work.

2. The method of making a" chaser from high speed steel, which comprises forming and cutting the threads of the chaser from unhardened material, subjecting the cut chasers to a temperature sufliciently hi h to cause partial melting of the points 0 the threads to harden the material, reducing the threads to approximate form, and then lapping the threads to a proper bearing on the work.

3. The method of making a chaser, which comprises cutting the chaser from unhardened material, hardening the material by a method producing distortion of thethreads of the chaser, grindin the threadsto approximately the desir'e form, and then la ping the threads to shape to bear proper y on the work.

form in which they bear properly on the work.

5. The method of finishing'a chaser, which comprises grinding the hardened threads thereof throughout their length to proper cross-section,'and then lapping the portions of said threads adjacent to their cutting edges to proper form to bear correctly on the work.

but the length of the threads of the hard- 6. The method of finishing a chaser, which comprises effecting a roughing cut throughened chaser, and then effecting a finishing out on the portions of the threads adjacent to their cutting edges to properly form them to bear correctly on the work.

In testimony wher'eof I have aflixed my signature. r

RALPH FLANDERS. 

